a good example for you:
friend of mine has been in this country since she was NINE MONTHS OLD. Ever since 1986. Hasn't left since. Grew up here, graduated with honors from HS, and is going to UC Berkeley.
Biggest reason why the process is hard, is because it is SO hard. In her case, her family applied for residency in 1996, when she was 10.
According to various immigration offices she's been to, the current cases and applications that the INS is looking at, for those coming from Mexico, are applications put in process in 1994. No joke. That's how slow the process is, let alone the amount of pre-reqs you need to put in an application in the first place.
In the meantime, she gets no financial aid, she barely makes enough to pay rent, and she's never been able to get a car, a job, an ID. The current system is all kinds of screwed up.